Neo down on compression

[Eager]

So following this thread

 I done a compression test and have found the cylinder against the bulkhead to be about 60 psi. It’s a unopened to my knowledge neo with a 3076 at 1.4 bar. Engine was cold, rest of cylinders are about 140

so, some more checks needed and will do a leak down test soon but in experience of others, Is this likely a piston issue or a valve or a gasket ?

engine runs and idles with no bad sounds etc, just lean and needs me to add fuel on the hand commander , this may or may not be connected. 

Many advise welcome

 

 

[KiwiRS4T]

Sadly likely to be a piston - possibly broken ring lands. RBs will run surprisingly well on 5 cylinders.  Yes do  a leak down test to confirm.

[Dose Pipe Sutututu]

Rebuild or Barra or JZ swap 

[Eager]

Yeh I’m prepared for a piston issue. It is what it is and at least if I forge I will get to run my turbo at a decent level of boost with some reliability. 

Lesk down test this week. 

[MrStabby]

Add 15ml of engine oil to 60psi cylinder and try again. If psi goes up, then its piston/ring of not its head/valve.

[Eager]

To follow this up

 

would one cylinder down to the 60psi, cause a lumpy running motor that reads very lean on wideband? Or is it possible I have a problem that caused the engine to run lean and then do the piston ?

when I up the fuel on the hand commander to 1:1.3 or so and bring the air/fuel ratio back towards what the normal readings were, the car idles and runs, quite healthy, but like a bag of crap when I just run it’s map at 1:1

so im trying to work out what has came first, is it a fuel problem that has caused lean running and melted a piston. Or is it the piston has failed and now not running right/firing properly on that one cylinder that it’s giving the lean reading

sorry if that is hard to understand 

Edited September 11, 2018 by Eager

[Dose Pipe Sutututu]

Do you have a wideband on it? You say it is running "lean" but do you actually have data?

Low comp, just add more boost and send it.

[Eager]

Yep I have wideband mate. Innovate. So can monitor things. It was running well, healthy, generally idled about 14.4 to 1. 

Then suddenly runs lumpy and reads about 17 or 18 to 1 once warmed up, needing some revs occasionally to keep it ticking over, 

but if I pick up the power F.C. hand commander and dump in fuel on the one time adjustment page and watch my air/fuel gauge slowly swing back, the idle sounds normal and happier, it takes up to about 1.2 or 1.3 of enrichment to start getting normal readings on the wideband gauge

 

im only talking about idle to keep my descriptions as easy as possible, but the problem is true across the Rev range, try to drive it and it feels like dragging a big anchor unless I dump that fuel in on power F.C. commander 

 

is this all symptoms of down on compression on one cylinder. Or is this a result of running lean possibly without me noticing and it’s done a piston and hence it’s now down to 60 on one cylinder ? Chicken and egg type thing 

Edited September 11, 2018 by Eager

[Dose Pipe Sutututu]

Could be a blocked/failing injector which also caused that cylinder to fail.

Problem with a single wideband is that it's reading an average of all 6 cylinders, I suggest take out your plugs and see the colour differences between them to determine which cylinder is leaner than the other (easiest option).

Best option is to remove the injectors and get them flow tested.

[Eager]

I pulled the plugs and they all looked very similar dude, and ye the average of all 6 cylinders doesn’t help a lot

 

they are very fresh r35 gtr factory injectors, would a item fail so early ? 

Having changed the pump the only other bits is, pump voltage regulator, fuel pressure regulator that’s factory or injectors or fuel filter(500 miles fresh z32 item)

Edited September 11, 2018 by Eager

[Dose Pipe Sutututu]

Anything new/old can fail unfortunately

[Eager]

That’s true.